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Date(s) - 27/09/2016
2:30 pm

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Will be held as stated below.

Date                  :     27 September, 2016 (Tuesday)
Time                  :     2.30 pm

Venue                 :     Lecture Hall 1, Block E07, FKM

Presenter             :    Dr. Muhammad Noor Afiq Witri bin Muhammad Yazid

Presentation Title    :     The Effects of Heating and Tree Configurations on Pollutant  Dispersion and Air Temperature in Street Canyon

Session Chairman      :     Assoc. Prof. Dr. Nor Azwadi Che Sidek

All staff are kindly invited. Thank you.


The Effects of Heating and Tree Configurations on Pollutant  Dispersion and Air Temperature in Street Canyon

Deterioration of outdoor air quality and harsh outdoor microclimate in street canyon posed a serious threat to urban dweller’s physical and mental health. In order to mitigate such undesired conditions, planting more trees and allowing more solar penetration into street canyon are highly recommended. However, both had contradictory effects on outdoor air quality and air temperature. The main purpose of this study was to investigate the combined effects of presence of trees, different diurnal heating situations and different street ratios on wind speed, pollutant dispersion and air temperature in a street canyon by means of Computational Fluid Dynamics (CFD). Initially, investigation on the suitability of the existing wind tunnel were carried out. The formation of a thick turbulent boundary layer in the wind tunnel had a good vertical mean velocity profile except for the turbulent intensity profile; hence an alternative wind tunnel study was adopted as benchmark data for CFD. Validation study of numerical simulation of wind flow in a street canyon under the influence of thermal effects shows that the prediction by the large eddy simulation (LES) against wind tunnel data was better than the Reynolds-averaged Navier-Stokes (RANS) at steady state and the unsteady RANS (URANS). In addition, qualitative comparison between the parameters that were adopted for parametric study against previous studies were adequately representing a street canyon at full scale. Based on rigourous parametric study, the street aspect ratio was identified as the dominant factor compared to the presence of trees in reducing wind speed (74% and 53%, respectively) and air quality (348% and 38.7%, respectively) in a street canyon because of low momentum transfer from ambient wind into lower region of street canyon. Furthermore, the presence of trees in a street canyon under different diurnal heating situations was regarded as an ideal condition to simultaneously achieve low air temperature and better air quality by trade-off between advantages and disadvantages of the respective factors. In this regard, the reduction of heated surface area and the buoyancy force produced in street canyon imposed by trees and diurnal heating situations, respectively could produce better air temperature and air quality compared to the worst case scenarios.